Various types of two-hand safety systems are used with hazardous, or potentially hazardous power tools of the electrical type. For example, a switch is connected to a mechanical linkage which permits operation of the switch if and only if two hand levers coupled to the linkage are simultaneously depressed, moved, or otherwise actuated. It has also been proposed to place two spatially separated switches in a circuit, both of which are spring-loaded, so that the electrical apparatus can be operated only if both switches are actuated against their spring loading which normally maintains them in OFF position. All such arrangements have the disadvantage that the position of the switches cannot be placed at random but is determined by the operating geometry and layout of the apparatus; in mechanical arrangements, particularly, the mechanical linkages and levers determine the placement of the operator's hands, so that ergometric considerations, and convenience of use cannot be fulfilled in many applications. Mechanical interlocks additionally have the disadvantage that they are subject to malfunction upon shock, contamination by dirt, and the like, and, similar to spring-loaded elements, have the further disadvantage that additional force must be applied by the operator which, over the period of a workday, is inconvenient and tiring. It has also been found in actual practice that many operators use ingenuity to override two-hand safety systems; mechanical switches, particularly, can often been overridden by unauthorized placement of metal bars, ropes, cables, or the like, so that the protective effort intended by the safety system is obviated.